Apheresis is a procedure in which an individual blood component can be separated and collected from whole blood withdrawn from a subject. Typically, whole blood is withdrawn through a needle inserted into the subject's arm and transferred into a cell separator, such as a centrifugal bowl. Once the whole blood is separated into its various components (e.g., plasma, red blood cells, and platelets), one or more of the components can be collected from the centrifugal bowl. The remaining components can be returned to the subject along with a compensation fluid to make up for the volume of the removed component.
While performing apheresis procedures, the technician must balance the procedure time with the safety of the patient. In particular, the technician must perform the procedure as quickly as possible to minimize the procedure time and associated discomfort of the subject, but must always be conscious of the safety of the subject. One such area for safety concern is the pressure at which the whole blood is withdrawn from the subject and the remaining blood components are returned to the subject. The pressure at which the remaining components and potential compensation fluid are returned to the subject is critical to the safety of the subject. If the pressure is too high during the return or too low in during the draw, the subject is at risk for vein lesions.
To control the pressure of the blood withdrawn from and components returned to the subject, current systems attempt to measure a venous pressure. However, current systems typically measure the pressure within the line at a distance away from the access site. This distance creates inaccuracies in the measurement and, as a result, current systems can not accurately measure the venous pressure. As one can imagine, these inaccuracies increase the risk to the patient and, perhaps, force the technician to operate the apheresis system at a non-optimized rate. Despite measuring as close as possible to the venipuncture, current systems do not factor in the loss of pressure that occurs between the point of measure and the tip of the needle,